Have you lost any data? If yes, it could be an issue with the drive. If no, try the following (extracted from Pbarney's thread):
1. Run CHKDSK /R /P from the recovery console (it will typically find no error)
2. run FIXBOOT from recovery console (typically has no result)
3. run FIXMBR from recovery console (typically has no result)
4. Run the manufacturer's diagnostic utility, downloaded from their website (it will typically find no error)
5. Changing the drives from cable select to Master/Slave may fix it.
6. Replacing the data cable may fix it, but usually not.
7. Setting the BIOS to use defaults may fix it, but usually not.
8. Changing the BIOS drive settings from auto to user-specified, ensuring that LBA is selected may fix it.
9. Pulling the CMOS battery to let the BIOS lose it settings may work.